1. Field of the Invention
The present invention relates to a semiconductor integrated circuit, a semiconductor integrated circuit module and an information apparatus, which utilize information concerning a time period and point.
2. Description of the Related Art
Semiconductor integrated circuits for use in information apparatuses are driven by electric power. Most information apparatuses are connected to an AC power supply via a cable, or to a battery, and power is supplied therefrom to semiconductor integrated circuits incorporated in the apparatuses.
On the other hand, some information apparatuses acquire power from electromagnetic waves, utilizing electromagnetic induction. This power is supplied to the semiconductor circuits incorporated therein to operate them. In light of the physical conformation or use, these information apparatuses are suitable for radio tags, non-contact IC cards, etc. that cannot incorporate batteries.
Radio tags and non-contact IC cards are equipped with an IC chip and antenna and no batteries. They are operated by an electromotive force that results from electromagnetic induction based on Fleming's law. Non-contact IC cards are of the same shape as standard magnetic cash cards. On the other hand, radio tags have various shapes. Non-contact IC cards or radio tags, called “a adjacent/vicinity type”, are accessible at a distance of approx. 1 m at maximum. Non-contact IC cards are standardized by ISO/IEC14443 (adjacent type) and ISO/IEC15693 (vicinity type). Most radio tags are based on these standards (see, for example, Jpn. Pat. Appln. KOKAI Publication No. 10-135882).
Typical systems utilizing such an information apparatus as the above are, for example, a shoplifting prevention system, in which a gate that generates electromagnetic waves is provided at the exit of a shop, and radio tags are attached to exhibited articles, or an automatic ticket gate system, in which automatic ticket checkers that generate electromagnetic waves are provided at ticket gates, and non-contact IC cards are used as commuter passes.
Information apparatuses utilizing electromagnetic induction by electromagnetic waves are not intended to always receive electromagnetic waves, but receive them only when necessary (only when they are used). In other words, the information apparatuses are not supplied with power when they are not used.
To control, for example, the period of use of an information apparatus that is supplied with power only when it is used, there were some methods, such as a method for managing the period of use at an apparatus that supplies electromagnetic waves, or a method for supplying time data together with electromagnetic waves to an information apparatus to enable it to use the time data. In both methods, the information apparatus depends on the power supply apparatus, which means that users of the power supply apparatus can illegally use the information apparatus by a simple modification of the power supply apparatus. Therefore, there is a need for a highly reliable semiconductor integrated circuit that enables information apparatuses to acquire correct time data used for control without depending on power supply apparatuses.